Display screen or portion thereof with a transitional graphical user interface



FIG. 1 is a front view of a display screen or portion thereof with a transitional graphical user interface, showing our new design, in accordance with a first embodiment and showing a first image thereof.

FIG. 2 is a front view of a second image thereof.

FIG. 3 is a front view of a third image thereof.

FIG. 4 is a front view of a fourth image thereof.

FIG. 5 is a front view of a fifth image thereof.

FIG. 6 is a front view of a sixth image thereof.

FIG. 7 is a front view of a seventh image thereof.

FIG. 8 is a front view of eighth image thereof.

FIG. 9 is a front view of a ninth image thereof.

FIG. 10 is a front view of a tenth image thereof.

FIG. 11 is a front view of a display screen or portion thereof with a transitional graphical user interface, showing our new design, in accordance with a second embodiment and showing a first image thereof.

FIG. 12 is a front view of a second image thereof.

FIG. 13 is a front view of a third image thereof.

FIG. 14 is a front view of a fourth image thereof.

FIG. 15 is a front view of a fifth image thereof.

FIG. 16 is a front view of a sixth image thereof.

FIG. 17 is a front view of a seventh image thereof.

FIG. 18 is a front view of eighth image thereof.

FIG. 19 is a front view of a ninth image thereof; and,

FIG. 20 is a front view of a tenth image thereof.

The appearance of the transitional graphical user interface sequentially transitions between the images shown in FIGS. 1-10 and between the images shown in FIGS. 11-20, respectively. The process or period in which one image transitions to another image forms no part of the claimed design.

The broken line showing of the display screen or portion thereof forms no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with a transitional graphical user interface, as shown and described. 